The siding has held up OK except in the front above the porch, which gets the morning sun. It is losing its paint. Is there a preferred method of dealing with this?
A: Yes there is. And for advice about anything paint, I turn to the experts at the Paint Quality Institute in Spring House, Pa.
First, how should you prepare old aluminum siding before painting? And what type of primer is the best for siding?
Remove as much chalk, dirt, and mildew as you can. Chalk is powdery pigment on the surface of weathered siding that comes off when you rub the palm of your hand over it.
Removal is done by power washing or by scrubbing and rinsing.
The only times a primer would be needed are if any bare aluminum is exposed or if there is still much chalk left on the surface.
In the first situation, remove any white oxide with a nonmetallic scouring pad, then wash off and rinse to make way for a latex corrosion-inhibitive primer. In the second scenario, apply a quality exterior alkyd — “oil-based” — primer recommended for aluminum siding by the manufacturer.
One consumer asked the institute experts whether he should wipe the siding with mineral spirits before priming, having had to use a sander to remove road salt from the surface that was now badly pitted.
The answer is no — unless you have some oily contaminant such as road tar on the siding. The road salt removed was probably white aluminum corrosion (aluminum oxide).
If you do prime everything, you will get a more uniform appearance from the paint, compared with if you only prime some parts.
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